1. Field of the Invention
This invention relates to cooling system cleaning formulations or flushes, and more specifically, to cleaning formulations without corrosion inhibitor packages which may be added to antifreeze/coolant compositions for rapid cleaning.
2. Description of the Prior Art
Antifreeze/coolants in North America generally use silicate based corrosion inhibitor packages. Silicates are particularly useful in protecting aluminum automotive cooling system components. The silicate corrosion inhibitors generally also use a phosphate, usually in the form of an alkali metal salt, to help protect metal cooling system parts and also as a buffer to control the pH of the coolant. Often phosphate salts are used to help maintain a stable alkaline environment from which multiple corrosion inhibitors can most effectively function.
Traditionally antifreeze/coolant is sold at nearly one-hundred percent glycol content. This concentrated packaging allows for flexibility so that the user can dilute the antifreeze/coolant, as needed, with available water to obtain the required freeze/boil protection.
In addition, during extended operation of the automotive cooling system, the corrosion inhibitor formulations in the antifreeze/coolant composition become depleted, thereby reducing corrosion inhibition. Once the corrosion inhibition packages cease functioning, corrosion product build up generally begins occurring on the metal surfaces of the cooling system. In addition, automotive oil and grease from contamination and leakage may also build up on the surfaces of the cooling system due to prolonged operation of the vehicle.
While corrosion inhibitor packages may be added to depleted antifreeze/coolant compositions to prolong the life of the antifreeze/coolant and to replenish corrosion inhibition properties, there remains a residual build up of oil, grease and corrosion products in the coolant system. A cleaning composition is generally needed to eliminate the build up of foreign substances in the coolant system.
Currently, most prior art cleaners contain chelators and corrosion inhibition packages. See, for example, U.S. Pat. Nos. 4,540,443; 5,062,987; and 5,071,582. The corrosion inhibition packages are designed to provide corrosion protection while the chelators clean the cooling system metal components. The balance between corrosion inhibition and metal cleaning requires that the cleaner be added and be maintained in the coolant system for a long period of time. Therefore, the cleaning component operates very slowly and remains in the system for an extended period of from hours to days.
These cleaners do not contain dispersants, such as polycarboxylates, to aid in the removal of particulate matter like hard water precipitates. Also, they neither address oil and grease removal nor the foaming tendency during engine application.
The use of EDTA, NTA, inorganic alkali metal phosphates and surfactants at a pH of 11 to 12.5 is disclosed to clean aluminum cars in U.S. Pat. No. 4,762,638. Such a formulation is too alkaline, and hence corrosive, for automobile cooling systems. In addition, there is no dispersant in the formulation.
U.S. Pat. No. 3,962,109 discloses an automotive cleaner plus inhibitor for cooling systems. The formulation is impregnated on a cooling system filter and is a permanent addition to the vehicle cooling system. The cleaner is never flushed out of the system and the filter is replaced every six months. U.S. Pat. No. 4,260,504 discloses deposit control additives for heat exchange systems, but does not involve cleaning or degreasing.
U.S. Pat. No. 4,363,741 discloses a rapid cooling system cleaner to remove rust scale and grease. The formulation consists of water, citric acid and oxypolyethoxyethanol as a surfactant at a pH of 4.5 to 8.5 and preferably 5.5 to 6.5. This formulation lacks a dispersant to aid particulate suspension and removal. U.S. Pat. No. 4,810,406 discloses a silicone silicate, phosphoric acid and water based cooling system treatment to dissolve corrosion and deposits. This patent does not have the capacity to remove grease and oil. In addition, the formulation contains no dispersant.
Certain polycarboxylate type materials have been disclosed for prevention of precipitates in antifreeze/coolant compositions. For example, U.S. Pat. No. 3,663,448 discloses scale inhibition for industrial cooling waters using amino phosphonate and polyacrylic acid compounds. U.S. Pat. No. 3,948,792 discloses an aqueous additive mixture to reduce and modify the amount of silicate scale formed in automotive cooling systems.
European patent 245557 discloses the use of a variety of compounds including sodium polyacrylate to prevent alkaline earth metal silicate precipitation. U.S. Pat. No. 4,487,712 discloses the use of polyacrylic acid as a silicate stabilizer to inhibit gelation. Gelation is a silicate depletion mechanism which can occur separately from hard water precipitates.
In spite of these disclosures, there remains a need for a rapid coolant system cleaning formulation that works quickly in the coolant system and is then removed.